Looks more like Ground Zero to me (Probably just one of Kojima teasers). Looks exactly like what what shown in the demonstration awhile back as well (Graphically, as well as the guy with the "covered eye").

IT is MGS game for sure ...another evidence is the hexagonal hospital bricks like those in VR missions or training...also KOjima Pro twitted screens from various surgical and medical items it has been rumored that it was a mini research for their upcoming game....

It makes sense, up until the point of the flaming whale & unicorn. Boss doesn't have a prosthetic arm. The correct eye is bandaged though. Personally, I think it's about cloning process, maybe this isn't Boss, maybe this is a facility full of faulty clones.

Right at the beginning, when the supposed Snake is looking at his prosthetic arm, the white leaves from the fight with The Boss in MGS3 are falling in front of him. To me, that was the immediate giveaway.